“People are consuming far more video on their smart phones, on their I-Pads,” says Clark. “And if we want to make smart decisions about how to allocate marketing dollars, we need to know what they’re watching and where.”

But there could be privacy concerns.

A Facebook spokesperson says the new system can’t be used to identify individuals. Even though Facebook and Nielsen announced the partnership last year, recent controversy over Facebook manipulating content to influence users’ emotions as part of a survey worries privacy advocates.